Approach to control over-etching of bottom spacers in vertical fin field effect transistor devices

ABSTRACT

A method of forming a vertical fin field effect transistor device, including, forming one or more vertical fins with a hardmask cap on each vertical fin on a substrate, forming a fin liner on the one or more vertical fins and hardmask caps, forming a sacrificial liner on the fin liner, and forming a bottom spacer layer on the sacrificial liner.

BACKGROUND Technical Field

The present invention generally relates to decreasing etchback of bottomspacers for vertical fin field effect transistors by using a sacrificialliner that provides increased selectivity for nitride etching processes,and more particularly to use of a germanium oxide sacrificial liner onvertical fin sidewalls that has a higher nitride etch rate in comparisonto silicon oxynitride.

Description of the Related Art

A Field Effect Transistor (FET) typically has a source, a channel, and adrain, where current flows from the source to the drain, and a gate thatcontrols the flow of current through the channel. Field EffectTransistors (FETs) can have a variety of different structures, forexample, FETs have been fabricated with the source, channel, and drainformed in the substrate material itself, where the current flowshorizontally (i.e., in the plane of the substrate), and FinFETs havebeen formed with the channel extending outward from the substrate, butwhere the current also flows horizontally from a source to a drain. Thechannel for the FinFET can be an upright slab of thin rectangularsilicon (Si), commonly referred to as the fin with a gate on the fin, ascompared to a MOSFET with a single gate in the plane of the substrate.Depending on the doping of the source and drain, an n-FET or a p-FET canbe formed.

Examples of FETs can include a metal-oxide-semiconductor field effecttransistor (MOSFET) and an insulated-gate field-effect transistor(IGFET). Two FETs also can be coupled to form a complementary metaloxide semiconductor (CMOS) device, where a p-channel MOSFET andn-channel MOSFET are coupled together.

With ever decreasing device dimensions, forming the individualcomponents and electrical contacts become more difficult. An approach istherefore needed that retains the positive aspects of traditional FETstructures, while overcoming the scaling issues created by formingsmaller device components.

SUMMARY

In accordance with an embodiment of the present invention, a method offorming a vertical fin field effect transistor device is provided. Themethod includes forming one or more vertical fins with a hardmask cap oneach vertical fin on a substrate, forming a fin liner on the one or morevertical fins and hardmask caps, forming a sacrificial liner on the finliner, and forming a bottom spacer layer on the sacrificial liner.

In accordance with another embodiment of the present invention, a methodof forming a vertical fin field effect transistor device is provided.The method includes forming a plurality of vertical fins with a hardmaskcap on each vertical fin on a substrate, forming a silicon oxide finliner on the plurality of vertical fins and hardmask caps, forming agermanium oxide sacrificial liner on the fin liner, and forming asilicon nitride bottom spacer layer on the sacrificial liner.

In accordance with another embodiment of the present invention, avertical fin field effect transistor device is provide. The vertical finfield effect transistor device includes one or more vertical fin(s) on asubstrate, a hardmask cap on each of the one or more vertical fin(s), abottom source/drain at the surface of the substrate, where at least aportion of the bottom source/drain is below at least one of the one ormore vertical fin(s), a silicon oxide fin liner on at least a portion ofthe bottom source/drain, a germanium oxynitride sacrificial liner on thefin liner, and a silicon nitride bottom spacer on the germaniumoxynitride sacrificial liner.

These and other features and advantages will become apparent from thefollowing detailed description of illustrative embodiments thereof,which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description will provide details of preferred embodimentswith reference to the following figures wherein:

FIG. 1 is a cross-sectional side view showing a plurality of verticalfins with a hardmask cap on each fin, in accordance with an embodimentof the present invention;

FIG. 2 is a cross-sectional side view showing a shield layer formed onthe exposed substrate surface, sidewalls and end faces of the verticalfin(s), and the hardmask cap on each vertical fin, in accordance with anembodiment of the present invention;

FIG. 3 is a cross-sectional side view showing the vertical fin(s) andthe hardmask cap(s) on the substrate after removal of the shield layer,in accordance with an embodiment of the present invention;

FIG. 4 is a cross-sectional side view showing a dielectric cover on thevertical fin(s) and the hardmask cap(s), in accordance with anembodiment of the present invention;

FIG. 5 is a cross-sectional side view showing the dielectric coverremoved from the exposed surfaces of the substrate, while remaining onthe sidewalls and end faces of the vertical fin(s) and hardmask cap(s),in accordance with an embodiment of the present invention;

FIG. 6 is a cross-sectional side view showing source/drain regionsformed at the surface of the substrate adjacent to the vertical fins, inaccordance with an embodiment of the present invention;

FIG. 7 is a cross-sectional side view showing source/drain regionsformed at the surface of the substrate adjacent to the vertical finsafter removal of the dielectric cover, in accordance with an embodimentof the present invention;

FIG. 8 is a cross-sectional side view showing a fin liner on thesidewalls of the vertical fins, in accordance with an embodiment of thepresent invention; and

FIG. 9 is a cross-sectional side view showing a sacrificial liner on thefin liner, in accordance with an embodiment of the present invention;

FIG. 10 is a cross-sectional side view showing a bottom spacer layerformed on the sacrificial liner, where the sacrificial liner has beenpartially converted to an oxynitride, in accordance with an embodimentof the present invention;

FIG. 11 is a cross-sectional side view showing expansion of thesource/drain regions into the regions below the vertical fins, inaccordance with an embodiment of the present invention;

FIG. 12 is a cross-sectional side view showing a portion of the bottomspacer layer removed from the vertical fins and hardmask caps, inaccordance with an embodiment of the present invention;

FIG. 13 is a cross-sectional side view showing a portion of thesacrificial oxynitride layer removed from the fin liner, in accordancewith an embodiment of the present invention;

FIG. 14 is a cross-sectional side view showing a portion of the finliner removed from the sidewalls of the vertical fins, in accordancewith an embodiment of the present invention;

FIG. 15 is a cross-sectional side view showing an insulating linerformed on the sidewalls of the vertical fins, and a gate dielectriclayer formed on the insulating liner, in accordance with an embodimentof the present invention;

FIG. 16 is a cross-sectional side view showing a work function layerformed on the gate dielectric layer, in accordance with an embodiment ofthe present invention;

FIG. 17 is a cross-sectional side view showing a conductive gate filllayer formed on the work function layer and gate dielectric layer, inaccordance with an embodiment of the present invention;

FIG. 18 is a cross-sectional side view showing removal of the conductivegate fill layer, work function layer, gate dielectric layer, andinsulating liner from the top surface of the hardmask caps, inaccordance with an embodiment of the present invention;

FIG. 19 is a cross-sectional side view showing partial removal of theconductive gate fill layer, in accordance with an embodiment of thepresent invention;

FIG. 20 is a cross-sectional side view showing partial removal of thework function layer, gate dielectric layer, and insulating liner fromthe side surface of the hardmask caps, in accordance with an embodimentof the present invention;

FIG. 21 is a cross-sectional side view showing a top spacer layer andILD layer formed on the conductive gate fill layer and hardmask caps, inaccordance with an embodiment of the present invention;

FIG. 22 is a cross-sectional side view showing the partial removal ofthe top spacer layer and interlayer dielectric (ILD) layer to expose thetop surface of the hardmask caps, in accordance with an embodiment ofthe present invention;

FIG. 23 is a cross-sectional side view showing the removal of thehardmask caps from the vertical fins, in accordance with an embodimentof the present invention;

FIG. 24 is a cross-sectional side view showing top source/drains on thevertical fins, in accordance with an embodiment of the presentinvention;

FIG. 25 is a cross-sectional side view showing ILD layer and top spacerlayer with a reduced height, in accordance with an embodiment of thepresent invention; and

FIG. 26 is a cross-sectional side view showing an additional ILD layerformed on the top spacer layer and top source/drains, in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION

Principles and embodiments of the present invention relate generally toa change in the protective liner material used to cover the verticalfin(s) of a fin field effect transistor device prior to formation of anitride bottom spacer. In various embodiments, a silicon oxide layer isat least partially replaced by a protective layer made of a materialthat has an increased etch rate after partial nitridation compared tosilicon oxynitride.

It has been found that use of a high density plasma (HDP) for formationof a silicon nitride bottom spacer layer of a finFET device can cause atleast partial nitridation of a silicon oxide (SiO) layer covering thesidewalls of a vertical fin to form silicon oxynitride (SiON). The etchrate of silicon oxynitride is closer to the etch rate of silicon nitride(e.g., Si₃N₄) than silicon oxide (e.g., SiO₂), so the conversion of theliner material during formation of a bottom spacer results in pooreretch selectivity between the liner and vertical fins and the bottomspacer, for example, during an etch-back process to remove the linerfrom the fin sidewalls. The reduction in selectivity makes it moredifficult to completely remove the liner material from the vertical finsidewalls without damaging and/or over-etching the bottom spacer witheither a SiConi™ etch process (i.e., remote plasma dry etch includingH₂, NF₃, and NH₃ plasma by-products) or a hydrogen fluoride etch (e.g.,aqueous hydrofluoric acid, hydrogen fluoride gas/plasma).

Typically the bottom spacer provides at least a portion of theelectrical insulation and physical separation between a bottomsource/drain and a gate structure on the vertical fin (an insulatinghigh-k dielectric layer may also be interposed between the conductivegate electrode and the bottom source/drain). Over-etching can cause areduction in the bottom spacer's resistivity, resulting in devicefailure due to shorting between the gate and bottom source/drain, andincreased parasitic capacitances between the gate electrode and thebottom source/drain. Each issue can degrade the overall deviceperformance.

Leaving a nitrided residue of the SiO liner on the vertical fin(s) cancause severe gate stack issues, for example, increased interface traps,inversion thickness, T_(inv), T_(oxgl) (the equivalent SiO₂ thicknessthat would result in the same gate leakage current as high-k gatedielectric material), and a high interface trap density, D_(it).

Principles and embodiments of the present invention relate generally toa simple and easy way to strip a sidewall fin liner utilizing the highselectivity etch rate of GeON/SiO₂ over the SiN bottom spacer.

Principles and embodiments of the present invention relate to formationof a sacrificial liner that can react with nitriding species duringformation of a bottom spacer to form an oxynitride that can subsequentlybe selectively removed without over etching the bottom spacer and finhardmask caps. Germanium oxide (GeO), aluminum oxide (e.g., AlO),lanthanum oxide (e.g., LaO), or combinations thereof, can be used toform germanium oxynitride (GeON), lanthanum oxynitride (LaON), andaluminum oxynitride (AlON). The oxide sacrificial liner (e.g., GeO₂) canoverlay a silicon oxide (SiO) liner to prevent nitridation of the SiO toSiON.

Principles and embodiments of the present invention also relate toformation of a bilayer protective liner on a vertical fin to ensurecomplete removal of the protective liner after formation of a siliconnitride bottom spacer using typical nitride etching processes (e.g.,SiConi™ etch or a hydrogen fluoride etch).

Exemplary applications/uses to which the present invention can beapplied include, but are not limited to: integrated semiconductordevices having FinFETs.

In various embodiments, the materials and layers can be deposited byphysical vapor deposition (PVD), chemical vapor deposition (CVD), atomiclayer deposition (ALD), molecular beam epitaxy (MBE), or any of thevarious modifications thereof, for example, plasma-enhanced chemicalvapor deposition (PECVD), metal-organic chemical vapor deposition(MOCVD), low pressure chemical vapor deposition (LPCVD), electron-beamphysical vapor deposition (EB-PVD), and plasma-enhanced atomic layerdeposition (PEALD). The depositions can be epitaxial processes, and thedeposited material can be crystalline. In various embodiments, formationof a layer may be by one or more deposition processes, where, forexample, a conformal layer can be formed by a first process (e.g., ALD,PEALD, etc.) and a fill can be formed by a second process (e.g., CVD,electrodeposition, PVD, etc.).

It should be noted that materials may be referred to only by theircomposition constituent, e.g., silicon, nitrogen, oxygen, carbon,hafnium, titanium, etc., without specifying a particular stoichiometry(e.g., SiGe, SiO₂, Si₃N₄, HfO₂, etc.) in recognition that thestoichiometry can vary based on formation processes, processingparameters, intentional non-stoichiometric fabrication, depositiontolerance, etc. Reference to only the composition constituents (e.g.,SiO, SiN, TiN, etc.) is, therefore, intended to refer to all suitablestoichiometric ratios for the identified composition.

It is to be understood that aspects of the present invention will bedescribed in terms of a given illustrative architecture; however, otherarchitectures, structures, substrate materials and process features andsteps can be varied within the scope of aspects of the presentinvention.

It should be noted that certain features may not be shown in all figuresfor the sake of clarity. This is not intended to be interpreted as alimitation of any particular embodiment, or illustration, or scope ofthe claims.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, a plurality of verticalfins with a hardmask cap on each fin is shown, in accordance with anembodiment of the present invention.

In one or more embodiments, one or more vertical fins 111 can be formedon a substrate 110, where the vertical fins 111 can be formed by asidewall image transfer (SIT) process.

In various embodiments, the vertical fins 111 can be formed by a doublepatterning process (e.g., sidewall image transfer (SIT)). In variousembodiments, the vertical fins 111 can be etched into the substrate 110or an epitaxial layer on the substrate by employing a lithographicpatterning process, a SIT process, (e.g., self-aligned quadruplepatterning (SAQP) or a self-aligned double patterning (SADP)), orepitaxially grown on the substrate.

In one or more embodiments, the SIT process can include forming ahardmask layer on the substrate 110, which can include an epitaxiallayer or active surface layer on the substrate, where the hardmask layercan define the location and dimensions of the vertical fin(s) 111 to beformed. The hardmask layer may be patterned and etched to form ahardmask cap 121 for each vertical fin. Patterning and etching of thehardmask into hardmask caps 121 can expose underlying portions of thesubstrate 110. The underlying portions of the substrate 110 can beremoved to form the one or more vertical fin(s) 111.

In one or more embodiments, the hardmask cap(s) 121 can be siliconnitride (SiN), a silicon oxynitride (SiON), a silicon carbonitride(SiCN), a silicon boronitride (SiBN), a silicon borocarbide (SiBC), asilicon boro carbonitride (SiBCN), a boron carbide (BC), a boron nitride(BN), or combinations thereof.

In one or more embodiments, the vertical fin(s) 111 can have a height inthe range of about 30 nm to about 100 nm, or in the range of about 30 nmto about 60 nm, or in the range of about 60 nm to about 100 nm, where aportion of the fin height can be covered by a gate structure.

In one or more embodiments, the vertical fin(s) 111 can have a width inthe range of about 5 nm to about 20 nm, or in the range of about 5 nm toabout 15 nm, or in the range of about 10 nm to about 15 nm, or in therange of about 10 nm to about 20 nm. In one or more embodiments, thevertical fin(s) 111 can have a length in the range of about 40 nm toabout 600 nm, or in the range of about 40 nm to about 200 nm, or in therange of about 200 nm to about 600 nm, although other lengths arecontemplated.

In various embodiments, the distance between adjacent vertical fins 111can be in the range of about 25 nm to about 80 nm, or in the range ofabout 25 nm to about 45 nm, or in the range of about 45 nm to about 80nm. In various embodiments, the smaller distance range between verticalfins 111 can provide for merging source/drains so multiple vertical fins111 can form a multiple vertical transport FET to enhance deviceperformance. The larger distance range between vertical fins 111 canprovide for single vertical fin devices without merged source/drains.Other layers may experience thickness variations with reduced verticalfin distances.

In one or more embodiments, a substrate 110 can be a semiconductor or aninsulator, or a combination of semiconductor and insulator with anactive surface layer (ASL) made of a semiconductor material. Variousportions of the substrate 110 can be crystalline, semi-crystalline,microcrystalline, or amorphous. The substrate can be essentially (i.e.,except for contaminants) a single element (e.g., silicon), primarily(i.e., with doping) of a single element, for example, silicon (Si) orgermanium (Ge), or the substrate can include a compound, for example,Al₂O₃, SiO₂, GaAs, SiC, or SiGe.

In one or more embodiments, the substrate 110 can have multiple materiallayers, for example, a semiconductor-on-insulator substrate (SeOI), asilicon-on-insulator substrate (SOI), germanium-on-insulator substrate(GeOI), or silicon-germanium-on-insulator substrate (SGOI), where anactive surface semiconductor layer of the substrate 110 can be on asubstrate insulator layer (e.g., buried oxide layer (BOX)). Thesubstrate 110 can also have other layers forming the substrate,including high-k oxides and/or nitrides. The substrate 110 can also haveother device structures such as isolation regions (e.g., shallow trenchisolation (STI) regions (not shown)). In one or more embodiments, asubstrate insulator layer (e.g., BOX layer) can be formed on at least aportion of a substrate 110.

In various embodiments, the substrate 110 may be a single crystalsilicon (Si), silicon-germanium (SiGe), or III-V semiconductor (e.g.,GaAs) wafer, or have a single crystal silicon (Si), silicon-germanium(SiGe), or III-V semiconductor (e.g., GaAs) active surface layer. In oneor more embodiments, the substrate 110 can be a silicon wafer.

In one or more embodiments, the vertical fin 111 can be formed on thesubstrate 110, where the vertical fin can be a strained vertical finmade of a semiconductor material. The vertical fin 111 can have atensile or compressive strain.

FIG. 2 is a cross-sectional side view showing a shield layer formed onthe exposed substrate surface, sidewalls and end faces of the verticalfin(s), and the hardmask cap on each vertical fin, in accordance with anembodiment of the present invention.

In one or more embodiments, a shield layer 130 can be formed on thesidewalls and end faces of the vertical fin(s) 111, as well as exposedportions of the substrate 110 and hardmask cap 121, where the shieldlayer 130 can be formed, for example, by in situ steam generation(ISSG), and the shield layer 130 can be a silicon oxide (e.g., SiO₂).The shield layer 130 can be used to remove damage from the etchedsurfaces and/or trim the vertical fin(s) 111 to adjust the findimensions.

FIG. 3 is a cross-sectional side view showing the vertical fin(s) andthe hardmask cap(s) on the substrate after removal of the shield layer,in accordance with an embodiment of the present invention.

In one or more embodiments, the shield layer 130 can be removed, forexample, using an isotropic etch, to expose the sidewalls and end facesof the vertical fin(s) 111, as well as the substrate surface andhardmask cap(s) 121.

FIG. 4 is a cross-sectional side view showing a dielectric cover on thevertical fin(s) and the hardmask cap(s), in accordance with anembodiment of the present invention.

In one or more embodiments, a dielectric cover 140 can be formed on thevertical fin(s) 111 and the hardmask cap(s) 121 to protect the verticalfin(s) during subsequent processing.

In various embodiments, the dielectric cover 140 can be silicon oxide(SiO), silicon nitride (SiN), a silicon oxynitride (SiON), a siliconcarbonitride (SiCN), a silicon boronitride (SiBN), a silicon borocarbide(SiBC), a silicon boro carbonitride (SiBCN), a boron carbide (BC), aboron nitride (BN), or combinations thereof, where the dielectric cover140 can be a different material from the hardmask cap(s) 121 to allowselective removal.

In a non-limiting exemplary embodiment, the dielectric cover 140 can besilicon oxide (SiO) formed by a conformal deposition (e.g., ALD, PEALD)to have a predefined thickness on the sidewalls and end faces of thevertical fin(s) 111. The thickness of the dielectric cover 140 candefine a distance from the base of a vertical fin 111 that a dopant canbe implanted into the substrate to form a source/drain region.

In one or more embodiments, the dielectric cover 140 can have athickness in the range of about 20 Å to about 100 Å, or in the range ofabout 40 Å to about 80 Å, or in the range of about 50 Å to about 60 Å,although other thicknesses are contemplated.

FIG. 5 is a cross-sectional side view showing the dielectric coverremoved from the exposed surfaces of the substrate, while remaining onthe sidewalls and end faces of the vertical fin(s) and hardmask cap(s),in accordance with an embodiment of the present invention.

In one or more embodiments, the portion of the dielectric cover 140 canbe removed from portions of the substrate surface to expose at least thesubstrate portions between and/or around the one or more vertical fin(s)111 for subsequent formation of source/drain region(s). The portions ofthe dielectric cover 140 can be removed, for example, by an etch-backprocess using a directional etching process (e.g., reactive ion etching(RIE)), while leaving a portion of the dielectric cover 140 on thevertical fin(s) 111 and hardmask cap(s) 121. A portion of the dielectriccover 140 on the hardmask cap(s) 121 may be removed at least from thesurfaces perpendicular to an impinging ion beam, where the tops of thehardmask cap(s) can become exposed.

FIG. 6 is a cross-sectional side view showing source/drain regionsformed at the surface of the substrate adjacent to the vertical fins, inaccordance with an embodiment of the present invention.

In one or more embodiments, source/drain regions 150 can be formedadjacent to the vertical fin(s) 111, where the source/drain regions 150can be formed in a portion of the substrate surface. In variousembodiments, n-type or p-type dopants can be implanted into portions ofthe substrate around and/or between each vertical fin 111. Dopants canbe incorporated during epitaxy (e.g., by in-situ epitaxy) of a surfacelayer on the substrate (e.g., an SiGe layer) or ex situ, where theincorporation can be by any suitable doping techniques, including butnot limited to, ion implantation, gas phase doping, plasma doping,plasma immersion ion implantation, cluster doping, infusion doping,liquid phase doping, solid phase doping, etc. In various embodiments,the source/drain regions 150 can be doped to form n-type or p-typesource/drains to fabricate NFETs or PFETs. In various embodiments, thesource/drain region(s) 150 can be formed into the substrate surface to adepth below the base of the vertical fin(s) 111, where an undoped regionmay remain after dopant implantation.

In one or more embodiments, the depth of the source/drain region 150into the surface of the substrate can be in the range of about 20 nm toabout 60 nm, or in the range of about 25 nm to about 35 nm, althoughother depths are contemplated.

In various embodiments, the depth of the source/drain region 150 intothe surface of the substrate can be sufficient to avoid an excessiveincrease in the resistance of the source/drain region 150 that wouldreduce device performance.

In various embodiments, there can be an undoped gap 112 in the substratesurface below the vertical fin(s) 111 between portions of thesource/drain regions 150. The width and length of the undoped gap 112can be greater than the width and length of the vertical fin 111 byabout twice the thickness of the dielectric cover 140, where thedielectric cover 140 can shadow a portion of the substrate directlyadjacent to the vertical fin. An undoped gap 112 can be under each ofthe vertical fin(s) 111.

FIG. 7 is a cross-sectional side view showing source/drain regionsformed at the surface of the substrate adjacent to the vertical finsafter removal of the dielectric cover, in accordance with an embodimentof the present invention.

In one or more embodiments, the dielectric cover 140 can be removed fromthe vertical fin(s) 111, where the dielectric cover 140 may be removedafter formation of the source/drain region(s) 150. In variousembodiments, the dielectric cover 140 can be removed by anon-directional isotropic etch selective for the material of thedielectric cover 140.

FIG. 8 is a cross-sectional side view showing a fin liner on thesidewalls of the vertical fins, in accordance with an embodiment of thepresent invention.

In one or more embodiments, an fin liner 160 can be formed on the one ormore vertical fin(s) 111, where the fin liner 160 can be formed on thesidewalls and end faces of the vertical fin(s) by a conformal deposition(e.g., ALD, PEALD, etc.). The fin liner 160 can also cover the exposedportion of the substrate 110 including source/drain region(s) 150.

In one or more embodiments, the fin liner 160 can be an oxide or acarbide, for example, silicon oxide (SiO), silicon carbide (SiC),silicon borocarbide (SiBC), boron carbide (BC), or a combinationthereof, where the fin liner 160 can be selectively removed relative toa bottom spacer and/or the hardmask cap(s) 121.

In one or more embodiments, the fin liner 160 can have a thickness inthe range of about 5 Å to about 20 Å, or about 8 Å to about 15 Å, orabout 10 Å.

In a non-limiting exemplary embodiments, the fin liner 160 can besilicon dioxide (SiO₂) having a thickness of about 10 Å.

FIG. 9 is a cross-sectional side view showing a sacrificial liner on thefin liner, in accordance with an embodiment of the present invention.

In one or more embodiments, a sacrificial liner 170 can be formed on thefin liner 160, such that the fin liner 160 is an inner liner and thesacrificial liner 170 is an outer liner. In various embodiments, thesacrificial liner 170 can be formed by a conformal deposition (e.g.,ALD, PEALD) on the exposed surfaces.

In one or more embodiments, the sacrificial liner 170 can have athickness in the range of about 5 Å to about 50 Å, or about 10 Å toabout 30 Å, or about 20 Å, where the sacrificial liner 170 can besufficiently thick to prevent nitridation of the underlying fin liner160. The sacrificial liner 170 can be thicker than the fin liner 160.

In one or more embodiments, the sacrificial liner 170 can be germaniumoxide (e.g., GeO₂), aluminum oxide (e.g., Al₂O₃), lanthanum oxide (e.g.,La₂O₃), or combinations thereof, where the sacrificial liner 170 canreact with a nitriding species during formation of a bottom spacer. In anon-limiting exemplary embodiment, the germanium oxide (GeO) can reactto form a germanium oxynitride (GeON).

In various embodiments, the fin liner 160 and sacrificial liner 170 canform a bilayer protective liner, where the fin liner 160 is an innerliner that can be directly on the sidewalls and end faces of a verticalfin 111, and the sacrificial liner 170 can be an outer liner on the finliner 160, where the surface of the outer sacrificial liner 170 could beexposed to the processing environment, for example, a nitridingatmosphere and/or plasma.

In a non-limiting exemplary embodiment, the bilayer protective liner caninclude a silicon dioxide (SiO₂) fin liner 160 having a thickness ofabout 10 Å, and a germanium dioxide (GeO₂) sacrificial liner 170 havinga thickness of about 20 Å on the fin liner 160.

FIG. 10 is a cross-sectional side view showing a bottom spacer layerformed on the sacrificial liner, where the sacrificial liner has beenpartially converted to an oxynitride, in accordance with an embodimentof the present invention.

In one or more embodiments, a bottom spacer layer 180 can be formed onthe sacrificial liner 170, where the bottom spacer layer 180 can bedirectionally deposited, for example by a high-density plasma (HDP)deposition, a gas cluster ion beam deposition (GCIB) or PVD, where thebottom spacer layer can have a greater thickness on surfacessubstantially perpendicular to the incident deposition species(horizontal surfaces as illustrated), and a lesser thickness on surfacessubstantially parallel to the incident deposition species (verticalsurfaces as illustrated).

In one or more embodiments, the bottom spacer layer 180 can be adielectric nitride compound, including, but not limited to siliconnitride (SiN), a silicon oxynitride (SiON), a silicon carbonitride(SiCN), a silicon boronitride (SiBN), and combinations thereof.

In one or more embodiments, the bottom spacer layer 180 can have athickness in the range of about 4 nm to about 10 nm, or in the range ofabout 4 nm to about 6 nm, although other thicknesses are contemplated.

In a non-limiting exemplary embodiment, the bottom spacer layer 180 canbe silicon nitride (Si₃N₄) formed by a high-density plasma deposition toa thickness of about 10 nm on the horizontal surfaces.

In one or more embodiments, the sacrificial liner 170 can react with thenitriding species forming the bottom spacer layer 180 to convert to anoxynitride layer 175, where the sacrificial layer can scavenge thenitriding species before it can react with the inner fin liner 160. Byreacting with nitriding species, the sacrificial liner 170 can preventthe fin liner from becoming an oxynitride (e.g., SiON). In variousembodiments, oxynitride layer 175 can have a thickness in the range ofabout 1 nm to about 3 nm.

In a non-limiting exemplary embodiment, a germanium oxide sacrificialliner 170 can react to form a germanium oxynitride sacrificial layer175. In various embodiments, the germanium oxynitride sacrificial layer175 can have a thickness in the range of about 1 nm to about 3 nm.

FIG. 11 is a cross-sectional side view showing expansion of thesource/drain regions into the regions below the vertical fins, inaccordance with an embodiment of the present invention.

In one or more embodiments, dopants can be diffused from thesource/drain regions 150 into the undoped gap(s) 112 below the verticalfin(s) 111 through a heat treatment (e.g., anneal). The dopants may alsodiffuse into a lower portion 157 of the vertical fin(s) 111, which canreduce the channel length of the vertical fins. In various embodiments,the heat treatment can also activate the dopants in the source/drainregions 150 to form active bottom source/drains 155 below each of theone or more vertical fin(s) 111. The source/drain regions can havesufficient dopant concentrations for diffusion.

In various embodiments, the active bottom source/drain 155 can span aplurality of vertical fins 111, such that two or more vertical fins 111can be electrically coupled to become part of the same vertical FinFETdevice.

In one or more embodiments, the source/drain regions 150 can be heattreated at a temperature in the range of about 900° C. to about 1100° C.

FIG. 12 is a cross-sectional side view showing a portion of the bottomspacer layer removed from the vertical fins and hardmask caps, inaccordance with an embodiment of the present invention.

In one or more embodiments, a portion of the bottom spacer layer 180 canbe removed to expose the sacrificial oxynitride layer 175 on thesidewalls of the vertical fin(s) 111 and hardmask caps 121, and the topsurface of the hardmask cap. A portion of the bottom spacer layer 180can be removed using a non-directional isotropic etch, such that thelesser thickness of the bottom spacer layer 180 on the perpendicularsurfaces would be removed from the bottom spacer layer 180 on thesubstrate to leave a reduced thickness bottom spacer 185 on portions ofthe substrate 110. In various embodiments, portions of the bottom spacerlayer 180 can be removed using either a SiConi™ etch process (i.e.,remote plasma dry etch including H₂, NF₃, and NH₃ plasma by-products) ora hydrogen fluoride etch (e.g., aqueous hydrofluoric acid, hydrogenfluoride gas/plasma). The etch rate of silicon nitride to silicon oxidecan be about 5 to 1, whereas the etch rate of silicon nitride togermanium oxynitride can be greater than 100 to 1, such that thesacrificial oxynitride layer 175 remains essentially unetched duringremoval of the bottom spacer layer 180.

In one or more embodiments, bottom spacers 185 can remain on thesacrificial oxynitride layer 175 on the substrate 110, where a portionof the bottom spacers 185 can be between the vertical fins 111. Thesacrificial oxynitride layer 175 can remain on the vertical fins 111 andhardmask caps 121, due to the etch selectivity of the SiConi™ etch orhydrogen fluoride etch for the nitride (e.g., Si₃N₄) of the bottomspacer layer.

FIG. 13 is a cross-sectional side view showing a portion of thesacrificial oxynitride layer removed from the fin liner, in accordancewith an embodiment of the present invention.

In one or more embodiments, the exposed portion of the sacrificialoxynitride layer 175 can be removed to expose the underlying fin liner160. In various embodiments, the sacrificial oxynitride layer 175 can beremoved by a buffered oxide etch (BOE), also referred to as a bufferedhydrogen fluoride etch (BHF), where the sacrificial oxynitride layer 175can be selectively removed over the nitride of the bottom spacers. Inthis manner, the thickness of the bottom spacers can be maintained.

In a non-limiting exemplary embodiment, an approximately 20 Å germaniumoxynitride layer (GeON) can be removed from a silicon dioxide (SiO₂) finliner 160 using a BOE with minimum change to the thickness of the bottomspacers 185.

FIG. 14 is a cross-sectional side view showing a portion of the finliner removed from the sidewalls of the vertical fins, in accordancewith an embodiment of the present invention.

In one or more embodiments, the fin liner 160 may also be removed fromthe vertical fins 111 and hardmask caps 121 using the same BOE used toremove the sacrificial oxynitride layer 175. Removal of both thesacrificial oxynitride layer 175 and fin liner 160 can expose thevertical fins 111 and hardmask fin caps 121.

In various embodiments, portions of the fin liner 160 and sacrificialoxynitride layer 175 can remain on the source/drains 185 at the surfaceof the substrate 110 and on the lower portions 157 of the vertical fins111.

FIG. 15 is a cross-sectional side view showing an insulating linerformed on the sidewalls of the vertical fins, and a gate dielectriclayer formed on the insulating liner, in accordance with an embodimentof the present invention.

In one or more embodiments, an insulating liner 190 can be formed on thevertical fins 111 and hardmask caps 121, where the insulating liner canbe formed by a conformal deposition on at least the sidewalls and endfaces of the vertical fins 111 and hardmask caps 121. The insulatingliner 190 can improve the gate stack properties.

In one or more embodiments, the insulating liner 190 can be siliconoxide (SiO), where the silicon oxide can be formed by ozone oxidation,thermal oxidation, chemical oxidation, plasma oxidation, etc.

In one or more embodiments, the insulating liner 190 can have athickness in the range of about 3 Å to about 20 Å, or in the range ofabout 5 Å to about 10 Å.

In one or more embodiments, a gate dielectric layer 200 can be formed onthe insulating liner 190 on the vertical fins 111. The gate dielectriclayer 200 can be formed by a conformal deposition (e.g., ALD, PEALD).

In various embodiments, the gate dielectric layer 200 can includesilicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON),boron nitride (BN), high-k dielectric materials, or any combination ofthese materials. Examples of high-k dielectric materials include, butare not limited to, metal oxides such as hafnium oxide (HfO), hafniumsilicon oxide (HfSiO), hafnium silicon oxynitride (HfSiON), lanthanumoxide (LaO), lanthanum aluminum oxide (LaAlO), zirconium oxide (ZrO),zirconium silicon oxide (ZrSiO), zirconium silicon oxynitride (ZrSiON),tantalum oxide (TaO), titanium oxide (TiO), barium strontium titaniumoxide (BaSrTiO), barium titanium oxide (BaTiO), strontium titanium oxide(SrTiO), yttrium oxide (YO), aluminum oxide (AlO), lead scandiumtantalum oxide (PbScTaO), and lead zinc niobate (PbZnNbO). The high-kmaterial can further include dopants such as lanthanum (La) and aluminum(Al).

In one or more embodiments, the gate dielectric layer 200 can have athickness in the range of about 5 Å to about 100 Å, or in the range ofabout 20 Å to about 50 Å.

FIG. 16 is a cross-sectional side view showing a work function layerformed on the gate dielectric layer, in accordance with an embodiment ofthe present invention.

In one or more embodiments, a work function layer 210 can be formed onthe gate dielectric layer 200 on at least a portion of the vertical fins111. The work function layer 210 can be formed by a conformal deposition(e.g., ALD, PEALD).

In various embodiments, the work function layer 210 can be a nitride,including but not limited to titanium nitride (TiN), hafnium nitride(HfN), hafnium silicon nitride (HfSiN), tantalum nitride (TaN), tantalumsilicon nitride (TaSiN), tungsten nitride (WN), molybdenum nitride(MoN), niobium nitride (NbN); a carbide, including but not limited totitanium carbide (TiC) titanium aluminum carbide (TiAlC), tantalumcarbide (TaC), hafnium carbide (HfC), and combinations thereof.

FIG. 17 is a cross-sectional side view showing a conductive gate filllayer formed on the work function layer and gate dielectric layer, inaccordance with an embodiment of the present invention.

In one or more embodiments, a conductive gate fill layer 220 can beformed in the remaining spaces between and around the vertical fins 111after formation of the gate dielectric layer 200 and work function layer210. In various embodiments, a gate structure can include the gatedielectric layer 200 formed on at least a portion of the insulatingliner 190 and the vertical fin 111, and a conductive gate electrodeincluding a conductive gate fill layer 220 and optionally a workfunction layer 210 between the gate dielectric layer 200 and theconductive gate fill layer 220.

In various embodiments, the conductive gate fill layer 220 can beblanket deposited to fill the spaces between the vertical fins 111,where the conductive gate fill layer 220 can extend above the topsurfaces of the work function layer 210 and/or gate dielectric layer 200on the hardmask caps 121.

In various embodiments, the conductive gate fill layer 220 material caninclude doped polycrystalline silicon (p-Si) or amorphous silicon(a-Si), germanium (Ge), silicon-germanium (SiGe), a metal (e.g.,tungsten, titanium, tantalum, ruthenium, zirconium, cobalt, copper,aluminum, lead, platinum, tin, silver, or gold), a conducting metalliccompound material (e.g., tantalum nitride (TaN), titanium nitride (TiN),tantalum carbide (TaC), titanium carbide (TiC), titanium aluminumcarbide (TiAlC), tungsten silicide (WSi), tungsten nitride (WN),ruthenium oxide (RuO), cobalt silicide (CoSi), or nickel silicide(NiSi)), carbon nanotube(s) (CNTs), conductive carbon, graphene, or anysuitable combination of these materials. The conductive gate fill layermaterial can further include dopants that are incorporated during orafter formation (e.g., deposition).

FIG. 18 is a cross-sectional side view showing removal of the conductivegate fill layer, work function layer, gate dielectric layer, andinsulating liner from the top surface of the hardmask caps, inaccordance with an embodiment of the present invention.

In one or more embodiments, a CMP can be used to remove a portion of theconductive gate fill layer 220, work function layer 210, gate dielectriclayer 200, and insulating liner 190 extending above the top surface ofthe hardmask caps 121 to provide a smooth, flat surface. The hardmaskcaps 121 can thereby be exposed, while the gate structure remains on thesidewalls of the hardmask caps and vertical fins 111.

FIG. 19 is a cross-sectional side view showing partial removal of theconductive gate fill layer, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a portion of the conductive gate fill layer220 can be selectively removed to reduce the height of the conductivegate fill layer 220, and thereby the gate structure on the vertical fins111. The height of the conductive gate fill layer 220 may be reduced toor below the level of the top surface of the vertical fin(s) 111, wherethe height of the conductive gate fill layer 220 may define a gatelength on the channel formed by the vertical fin 111.

FIG. 20 is a cross-sectional side view showing partial removal of thework function layer, gate dielectric layer, and insulating liner fromthe side surface of the hardmask caps, in accordance with an embodimentof the present invention.

In one or more embodiments, a portion of the work function layer 210,gate dielectric layer 200, and insulating liner 190 can be selectivelyremoved to reduce the height of the gate structure on the vertical fins.The height of the work function layer 210, gate dielectric layer 200,and insulating liner 190 may be reduced to the level of the top surfaceof the conductive gate fill layer 220 and/or vertical fin(s) 111, todefine a gate length on the channel formed by the vertical fin 111. Thework function layer 210, gate dielectric layer 200, and insulating liner190 can be removed by an isotropic etch, where each layer may be removedby a separate etch.

FIG. 21 is a cross-sectional side view showing a top spacer layer andILD layer formed on the conductive gate fill layer and hardmask caps, inaccordance with an embodiment of the present invention.

In one or more embodiments, a top spacer layer 230 can be formed on theconductive gate fill layer 220 and the hardmask caps 121, where the topspacer layer 230 can be formed by a conformal deposition to control thetop spacer layer thickness. The top spacer layer 230 can also cover theexposed edges of the work function layer 210, gate dielectric layer 200,and insulating liner 190.

In one or more embodiments, the top spacer layer 230 can be a siliconboronitride (SiBN), a silicon borocarbide (SiBC), a silicon borocarbonitride (SiBCN), a boron carbide (BC), a boron nitride (BN), orcombinations thereof. The top spacer layer 230 can be a differentmaterial from the hardmask caps 121, such that the hardmask caps 121 canbe selectively removed without removing the adjacent top spacer layer230.

In one or more embodiments, an interlayer dielectric (ILD) layer 240 canbe formed on the top spacer layer 230, where the ILD layer 240 can beformed by a blanket deposition on the top spacer layer.

In various embodiments, the ILD layer 240 can be silicon oxide (SiO), alow-K insulating dielectric, silicon oxynitride (SiON), carbon dopedsilicon oxide, fluorine doped silicon oxide, boron carbon nitride,hydrogen silsesquioxane polymer (HSQ), methyl silsesquioxane polymer(MSQ), methyl doped silica or SiOx(CH₃)y or SiC_(x)O_(y)H_(z),organosilicate glass (SiCOH), porous SiCOH, and/or combinations thereof.Excess ILD material may be etched back or removed by chemical-mechanicalpolishing (CMP), where the chemical-mechanical polishing can provide asmooth flat surface.

FIG. 22 is a cross-sectional side view showing the partial removal ofthe top spacer layer and interlayer dielectric (ILD) layer to expose thetop surface of the hardmask caps, in accordance with an embodiment ofthe present invention.

In various embodiments, the portion of the ILD layer 240 and top spacerlayer 230 can be removed from the top surface of the hardmask cap(s)121, where the ILD layer 240 and top spacer layer 230 can be etched backand/or removed using CMP. The top surface of the hardmask cap(s) 121can, thereby, be exposed.

FIG. 23 is a cross-sectional side view showing the removal of thehardmask caps from the vertical fins, in accordance with an embodimentof the present invention.

In one or more embodiments, the hardmask cap(s) 121 can be selectivelyremoved from the tops of the vertical fin(s) 111, for example, by aselective RIE or wet etch to form openings 125. The top surfaces of thevertical fin(s) 111 can thereby be exposed.

FIG. 24 is a cross-sectional side view showing top source/drains on thevertical fins, in accordance with an embodiment of the presentinvention.

In one or more embodiments, top source/drains 250 can be formed on thetop surfaces of the vertical fins 111, where the top source/drains 250can be epitaxially grown on crystalline vertical fins. The top surfacesof the vertical fins can have a predetermined crystal face. The topsource/drains 250 can be formed with a predetermined crystal orientationbased on the exposed crystal face of the vertical fin 111.

In one or more embodiments, the top source/drain(s) 250 can be in-situdoped (where doping and epitaxy growth are performed at the same time),and/or ex-situ doped (where doping occurs before and/or after epitaxy).Dopants can be incorporated during epitaxy (e.g., by in-situ epitaxy) orby any other suitable doping techniques, including but not limited to,ion implantation, gas phase doping, plasma doping, plasma immersion ionimplantation, cluster doping, infusion doping, liquid phase doping,solid phase doping, etc. In various embodiments, the source/drains 250can be doped to form n-type or p-type source/drains to fabricate NFETsor PFETs. Although the top surface of the source/drain(s) 250 aredepicted as below the top surface of the ILD layer 240 and top spacerlayer 230 the top source/drains 250 can also be coplanar with, inbetween, or above the top surface of the ILD layer 240 depending on theextent of the epitaxial growth. The top source/drains 250 can be formedin openings 125.

FIG. 25 is a cross-sectional side view showing ILD layer and top spacerlayer with a reduced height, in accordance with an embodiment of thepresent invention.

In one or more embodiments, a portion of the ILD layer 240 and topspacer layer 230 can be removed to reduce the height to approximatelythe level of the top source/drains 250. In various embodiments, theheight of the ILD layer 240 and top spacer layer 230 can be reducedusing CMP.

FIG. 26 is a cross-sectional side view showing an additional ILD layerformed on the top spacer layer and top source/drains, in accordance withan embodiment of the present invention.

In one or more embodiments, an additional ILD layer 245 can be formed onthe ILD layer 240 already present, and on the top source/drains 250 andexposed portions of the top spacer layer 230, prior to conducting backend of line (BEOL) processes to form electrical connections to the topsource/drains 250, bottom source/drains 155, and gate electrodes.Formation of the additional ILD layer 245 can provide a thicker ILDlayer on the FinFET device components.

It will also be understood that when an element such as a layer, regionor substrate is referred to as being “on” or “over” another element, itcan be directly on the other element or intervening elements can also bepresent. In contrast, when an element is referred to as being “directlyon” or “directly over” another element, there are no interveningelements present. It will also be understood that when an element isreferred to as being “connected” or “coupled” to another element, it canbe directly connected or coupled to the other element or interveningelements can be present. In contrast, when an element is referred to asbeing “directly connected” or “directly coupled” to another element,there are no intervening elements present.

The present embodiments can include a design for an integrated circuitchip, which can be created in a graphical computer programming language,and stored in a computer storage medium (such as a disk, tape, physicalhard drive, or virtual hard drive such as in a storage access network).If the designer does not fabricate chips or the photolithographic masksused to fabricate chips, the designer can transmit the resulting designby physical means (e.g., by providing a copy of the storage mediumstoring the design) or electronically (e.g., through the Internet) tosuch entities, directly or indirectly. The stored design is thenconverted into the appropriate format (e.g., GDSII) for the fabricationof photolithographic masks, which typically include multiple copies ofthe chip design in question that are to be formed on a wafer. Thephotolithographic masks are utilized to define areas of the wafer(and/or the layers thereon) to be etched or otherwise processed.

Methods as described herein can be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case, the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case, the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

It should also be understood that material compounds will be describedin terms of listed elements, e.g., SiGe. These compounds includedifferent proportions of the elements within the compound, e.g., SiGeincludes Si_(x)Ge_(1-x) where x is less than or equal to 1, etc. Inaddition, other elements can be included in the compound and stillfunction in accordance with the present principles. The compounds withadditional elements will be referred to herein as alloys.

Reference in the specification to “one embodiment” or “an embodiment”,as well as other variations thereof, means that a particular feature,structure, characteristic, and so forth described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “in one embodiment” or “in an embodiment”, as well anyother variations, appearing in various places throughout thespecification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following “/”,“and/or”, and “at least one of”, for example, in the cases of “A/B”, “Aand/or B” and “at least one of A and B”, is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of both options (A andB). As a further example, in the cases of “A, B, and/or C” and “at leastone of A, B, and C”, such phrasing is intended to encompass theselection of the first listed option (A) only, or the selection of thesecond listed option (B) only, or the selection of the third listedoption (C) only, or the selection of the first and the second listedoptions (A and B) only, or the selection of the first and third listedoptions (A and C) only, or the selection of the second and third listedoptions (B and C) only, or the selection of all three options (A and Band C). This can be extended, as readily apparent by one of ordinaryskill in this and related arts, for as many items listed.

The terminology used herein is for the purpose of describing particularembodiments only and is not tended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural tonus as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like, can be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the FIGS. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the FIGS. For example, if the device in theFIGS. is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device can be otherwise oriented (rotated 90degrees or at other orientations and the spatially relative descriptorsused herein can be interpreted accordingly. In addition, be understoodthat when a layer is referred to as being “between” two layers, it canbe the only layer between the two layers, or one or more interveninglayers can also be present.

It will be understood that, although the terms first, second, etc. canbe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first element discussed belowcould be termed a second element without departing from the scope of thepresent concept.

Having described preferred embodiments of a device and fabricationmethod (which are intended to be illustrative and not limiting), it isnoted that modifications and variations can be made by persons skilledin the art in light of the above teachings. It is therefore to beunderstood that changes may be made in the particular embodimentsdisclosed which are within the scope of the invention as outlined by theappended claims. Having thus described aspects of the invention, withthe details and particularity required by the patent laws, what isclaimed and desired protected by Letters Patent is set forth in theappended claims:

What is claimed is:
 1. A method of forming a vertical fin field effecttransistor device, comprising: forming one or more vertical fins with ahardmask cap on each vertical fin on a substrate; forming a fin liner onthe sidewalls of the one or more vertical fins and hardmask caps;forming a sacrificial liner on the fin liner, wherein the sacrificialliner is a material that reacts with a nitriding species; and forming abottom spacer layer on the sacrificial liner, wherein the bottom spacerlayer is formed using a nitriding species that reacts with thesacrificial liner.
 2. The method of claim 1, wherein the sacrificialliner is germanium oxide.
 3. The method of claim 2, wherein thesacrificial liner has a thickness in the range of about 5 Å to about 50Å.
 4. The method of claim 2, wherein the fin liner is silicon oxide. 5.The method of claim 2, wherein the bottom spacer layer is formed by ahigh-density plasma (HDP) deposition.
 6. The method of claim 5, whereinthe bottom spacer layer is silicon nitride.
 7. The method of claim 5,wherein the high-density plasma (HDP) deposition converts at least aportion of the germanium oxide to germanium oxynitride.
 8. The method ofclaim 1, further comprising forming one or more source/drain regions atthe surface of the substrate, and heat treating the source/drain regionsto form active bottom source/drains.
 9. The method of claim 8, furthercomprising removing a portion of the bottom spacer layer after heattreating the source/drain regions to form active bottom source/drains.10. The method of claim 9, further comprising removing an exposedportion of the reacted sacrificial liner after removing a portion of thebottom spacer layer.
 11. A method of forming a vertical fin field effecttransistor device, comprising: forming a plurality of vertical fins witha hardmask cap on each vertical fin on a substrate; forming a siliconoxide fin liner on the sidewalls of the plurality of vertical fins andhardmask caps; forming a germanium oxide sacrificial liner on the finliner; and forming a silicon nitride bottom spacer layer on thesacrificial liner, wherein the silicon nitride bottom spacer layer isformed by a high-density plasma (HDP) deposition.
 12. The method ofclaim 11, further comprising forming a bottom source/drain below each ofthe plurality of vertical fins, and removing a portion of the bottomspacer layer to form bottom spacers adjacent to each of the plurality ofvertical fins.
 13. The method of claim 12, further comprising forming agate structure on each of the plurality of vertical fins, where eachgate structure is on at least one bottom spacer.
 14. The method of claim13, further comprising removing the hardmask cap from each of theplurality of vertical fins, and forming a top source/drain on each ofthe plurality of vertical fins.
 15. The method of claim 13, furthercomprising forming a top spacer layer on the gate structures, whereinthe top spacer layer is silicon boro carbonitride (SiBCN).